You're right that there is no specialised "when you sneak or hide…" move. What you do is listen to whatever the player wants to do, and see what move that would be.
Sometimes it will fall under "Tricks of the trade": picking pockets is listed, and I would allow the player to let that DEX roll cover the entire act of sneaking up to someone in order to pick their pocket. Sometimes it will be Defying Danger: if you're hunted by goblins down the corridor and you want to disappear into the shadows, you're defying the danger by getting out of the way, so roll+DEX.
Say you enter a castle through the window using a grapple hook and want to make it to the throne room without being noticed. The GM might simply decide, depending on how often the guards patrol, that it's no problem for you as long as you take it slow and stick to the shadows. Or they might say that everything's fine until this one moment where you turn a corner and catch a glimpse of the light of a guard's torch before you duck back behind the corner, what do you do? As in, most of the sneaking is okay but there's this one time i's put to the test.
Or maybe they just say that you're obviously spending a moment to survey this dangerous area, so roll+DEX for "Trap sense". "Is there a trap here and if so, what activates it" works perfectly well for patrolling guards. "What else is hidden here" might find you a good hiding spot that means you don't have to roll to hide there – you just do it.
In general, quite a few situations with sneaking are pretty binary in that either you have a hiding place or safe path to sneak on, or you don't, and the skill of the sneaker lies in finding these, either beforehand (trap sense, discern realities) or just when needed (Defying danger by getting out of the way, acting fast, or quick thinking, i.e. DEX or INT). And the thief wants high DEX, so they'll be good at that anyway.